Basically the only "stdlib" that Fortran gives you are some mathematical functions, super basic string and file operations and that's it. There are no APIs for networking, sockets, IPC, threads, etc. that pretty much al modern languages come with.

Can you write a parser in it? Sure, but it's going to be painful dealing with strings. Can you write a web server? Yes, but you'd have to link to a C library that exposes the kernel TCP/IP interface to Fortran. And so, on.

So, essentially it would be like using C without a libc: it's doable, but it doesn't really make sense.